<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  
  <style>
    html,body{
      width: 100%;
      height: 100%;
      margin: 0;
    }
    #cesiumContainer{
      width: 100%;
      height: 100%;
    }
  </style>
</head>
<body>
  <div id="cesiumContainer"></div>
  <script src="js/demo.js"></script>
 </div>
</body>
</html>